If you’re the Celtics, and you’re facing the much-despised Heat, there is not a whole lot of room for moral victories. They were without Kevin Garnett in Monday’s 105-103 loss to Miami at the TD Garden, but that fact, and the fact that they actually held a 13-point lead with 8:27 to play, isn’t much consolation.

But one bright spot that should be celebrated in Boston is the performance of forward Jeff Green, who got the start in Garnett’s place. Green had easily the best game of his stint with the Celtics, and arguably the best game of his NBA career, scoring 43 points on 14-for-21 shooting, with seven rebounds and four blocked shots.

“Jeff was terrific,” Celtics coach Doc Rivers said. “I thought he played well the entire night. He attacked. You know what I loved about Jeff, I thought the first two minutes of the game, three minutes of the game, he was struggling. He missed a free throw, missed a couple of shots. And you know the old Jeff may have gone away. He actually just kept going and kept going, and that’s all we talked about. And once he realized he had an advantage, he took advantage. And that was great.”

When Rivers references the “old Jeff,” he means the one that has had a hard time fitting in with his Hall of Fame Celtics teammates. When the Celtics traded for Green in 2011, getting him from Oklahoma City in a deal for Kendrick Perkins, they were expecting him to blossom into a do-it-all sixth man in the mold of the old Lamar Odom. He was averaging 15.2 points with the Thunder, showing the ability to play some power forward, some small forward and even a bit of shooting guard.

Instead, Green seemed overwhelmed by playing with Garnett, Paul Pierce and Ray Allen, and was far too reluctant to get his own shots. Rivers had hoped that would change last year but Green was dealt a difficult setback before the season when he learned he had an aneurysm in his aorta and would need open-heart surgery. He missed the entire year.

In the offseason Green was a free agent, and Celtics president Danny Ainge took a risk by granting him a four-year contract worth $36 million. Green’s health was not expected to be an issue, but his performance was a real question—he had averaged just 9.8 points in the 26 games he played with Boston, and only 7.3 points in nine playoff games.

To start the year, Green still looked tentative. Rivers stayed on him to be more aggressive—especially with Allen gone to Miami, the Celtics would need production from Green to be competitive this year. When Rajon Rondo and Jared Sullinger went out with injuries, Green almost had no choice but to assert himself more.

In his last 24 games, going back to just before Rondo was hurt, Green has been the player Ainge thought he was signing. He is averaging 15.7 points, shooting 50.0 percent from the field and 40.0 percent from the 3-point line.

Though Green’s remarkable performance came in a loss, he at least can take some positives from it, knowing the Celtics nearly beat the Heat even without Garnett. “It was the best team in the league and we took them to their breaking point,” Green said. “We have just got to, when Kevin comes back, continue to play like we did today. With the addition of him, I think we will be more lethal. So as long as we continue to attack, get stops, we’ll be in pretty good shape.”